Certain cold wax depilatory compositions (which are not transparent) have been disclosed by the present inventor in U.S. patent application Ser. No. 10/248,925 filed Mar. 3, 2003.
Various compositions and methods for removing hair (depilation) are known. For example, hair can be removed by electrolysis, by chemical action, or by physical removal. Various depilatory compositions, which utilize physical removal action, are described in, for example, U.S. Pat. Nos. 6,478,493; 5,847,363; 5,698,187; 5,848,850; 5,846,326; 5,158,765; 5,154,919; 5,840,765; 5,470,563; 5,154,919; 4,832,949; 2,091,313 and U.S. Patent Application 20030002912, among others.
Physical removal generally involves the use of wax or tacky tape. Generally, two types of wax for depilatory purposes are used for hair removal, a hot wax or a cold wax. Cold wax is gummy at room temperature, whereas hot wax is hard to medium hard at room temperature.
The hot wax compositions are typically heated above their melting point and coated onto the skin. Upon solidification, hair becomes trapped in the wax and is removed when the wax is peeled off the skin. During this process, some epidermal layers of skin are also removed or stripped away, exposing lower layers of skin and initiating inflammatory reaction from prostaglandin's formation. This is the principal reason for the development of skin irritation caused by the hot wax compositions. This fact has not been recognized by prior art. For example, prior art has focused mainly on the use of anti-irritants to circumvent this problem of skin irritation, as disclosed in U.S. Pat. No. 5,470,563 (Tanaka et al.).
In order to solve the problem of damage to skin from such heated depilatory compositions, several “cold-wax” hair removal compositions have been disclosed. Cold wax compositions do not require such a pre-heating or microwave step prior to their application for depilation. However, most such cold wax compositions are based on sugar or sugar derivatives. For example, U.S. Pat. No. 5,158,765 (Qasem) discloses a depilatory composition for the removal of hair that is composed of a mixture of sugar, water and aspirin. This mixture is heated to dissolve the solute materials, and then allowed to cool so as to form a soft, pliable composition that can be manually applied to the skin. The composition firmly adheres to the hair with which it comes in contact, and by quickly drawing the applied material away from the skin, will cause the hair to be removed from its roots. One problem from such compositions that are directly applied to skin is that usually an area larger than the area where depilation is needed is coated with such compositions, requiring a more extensive cleanup step after hair removal. Another problem is that such cold-wax compositions based on sugar or sugar derivatives do not remove all the hair in a single step, requiring two or more applications in the same area. This causes waste of product, additional skin irritation, and inconvenience.
Among other similar sugar-based compositions, U.S. Pat. No. 5,698,187 (Naggiar) discloses depilatory composition for the removal of hair from the human body that is composed of a mixture of maltodextrin, sucrose, water and citric acid. This mixture is heated to dissolve the solute materials, and then cooled to form a soft, pliant composition, which can be manually applied to the skin.
U.S. Pat. No. 4,842,610 (Gordon et al.) discloses hair removal compositions that comprise 90 to 99.5% corn syrup and 0.5% to 10% added water by weight. The compositions are used by applying them to the surface of the skin in a hairy area, pressing a sheet of paper or other fibrous material against the area and subsequently lifting the sheet of fibrous material or peeling it off the skin surface.
U.S. Pat. No. 4,832,949 (Royal) discloses a depilatory composition for removal of hair from the human skin that is made up of a mixture of honey, sugar and citric acid which mixture is heated to a predetermined temperature level, then allowed to cool so as to form a highly viscous, wax-like composition which can be applied manually in slender strips to the skin.
It is commonly recognized that sugar-based compositions do not remove hair adequately in a single application, as mentioned above. The most preferred depilatory compositions are based on rosin or rosin derivatives, or polymers. However, such compositions must be applied in hot state, causing the problems of inconvenience, burns, skin irritation, extensive cleanup after use, and such as mentioned earlier. Sugar and sugar derivatives based compositions, on the other hand, contain substantial amounts of water, or alcohol, or mixtures of water and alcohol, which tend to evaporate each time a bottle is opened for product application, thus resulting in the crystallization of sugar or sugar derivatives from such compositions. Such crystallizations cause a loss of the hair removing power of such compositions, and also make it harder for the bottle to be opened for product use. U.S. Pat. No. 6,417,346 (Salome et al.) further discusses such sugar solution crystallization problems. Additionally, a “dry-down” period is required for such sugar and sugar derivatives based compositions after product applications to let water or alcohol partially evaporate, and before the depilation step is completed. This “dry-down” period can be from 5 minutes to 20 minutes, or even longer. The product does not gain sufficient “stickiness” to remove hair if this “dry-down” period is not observed.
Most hot wax compositions are opaque and not elegant in appearance or application on skin. For example, they cannot be made in different colors, or contain mica and other visually appealing compositions to give a shiny, brilliant appearance with particles suspended and visible in a three-dimensional manner.
Some cold wax compositions can be made in transparent form. However, they are mostly made from sugar and sugar derivatives that lack hair removal efficacy in a single application. Also, the rheological properties of such compositions do not permit the inclusion of visibly attractive particles or additives that can remain suspended in a three-dimensional manner in a stable composition. Most sugar and sugar derivatives based transparent compositions are greatly sensitive to storage temperature conditions that frequently result in the re-agglomeration of any suspended particles included in such compositions for visual aesthetics.
Also, as mentioned earlier, the skin irritation is caused mostly by the stripping of the upper layers of skin from such sticky depilatory compositions of both hot wax and cold wax forms. It would be ideal if such compositions can adhere preferentially to hair, and not skin. Although not bound by any theory, it should be possible to achieve this in such a selective manner.
It is well known that hair possesses more hydrophobic properties than skin. Hair is more tightly composed due to the presence of sulfur amino acids (cysteine and cystine) in its keratin structure. Skin, on the other hand, is known to contain a large amount of hydrophilic amino acids. If a depilatory composition can be devised to bond more strongly with hydrophobic groups of hair and cause less strong bonding with skin surface taking advantage of skin's more hydrophilic surface, then such a bonding would provide more selective adherence to hair surface, thus causing hair removal much easier, and causing much less disruption of the upper layers of skin.
In addition, most current manufacturing procedures for both cold wax and hot wax compositions require heating of a mixture of solid and liquid components at the dissolution temperatures of the solid components in the liquid components. Such temperatures usually exceed 100° C. for prolonged period of time till such dissolutions are complete. These compositions must be constantly mixed during this time. It is also frequent that the total solid components in such compositions are more predominant, usually in excess of 80%. This makes the mixing process very difficult for such compositions. Additionally, such high temperatures and prolonged periods of heating during the manufacturing process cause significant degradation, oxidation, and discoloration of components. It is also difficult to add perfumes, colorants, and many visually attractive ingredients in such compositions due to such high temperature requirements.
It would thus be advantageous to devise manufacturing processes for both cold wax and hot wax compositions that require much lower temperatures for processing, for example, not exceeding 80° C., and also contain a greater amount of liquid components to improve mixing process. It would be preferred to have at least 30% of total liquid components in such compositions for industrially convenient manufacturing process.
It would thus be advantageous if a depilatory composition can be made that has the following properties: (1) It is transparent in appearance, and (2) It can be made in either cold wax or hot wax forms, and (3) It is manufactured at much less than 100° C., and (4) Three-dimensional colored or shiny particles made of plastic, mica, metal, ceramic, cloisonn é, and other visually attractive compositions can be added that remain stable under the conditions of storage and use, and (5) It can bind more strongly with hair and less strongly with skin, and (6) It can be applied either directly on the skin or applied on a piece of fabric, plastic, or paper first, which is then applied to skin for hair removal, and (7) Require minimal clean-up, and (8) Additional skin and hair beneficial ingredients, such as hair growth retardants, anti-irritants, topical pain relief agents, antioxidants, skin soothing agents, skin cooling agents, emollients, moisturizers, topical anesthetics, colorants, botanical extracts, fragrances, and such can be included.